The third diagram, Figure REF , starts with the
primal–dual three-operator (PD3O) splitting algorithm [1]}
\(x^{(k+1)} &= \mathrm {prox}_{\tau f} (x^{(k)}-\tau (A^Tz^{(k)}+\nabla h(x^{(k)}))) \\z^{(k+1)} &= \mathrm {prox}_{\sigma g^\ast }(z^{(k)}+\sigma A(2x^{(k+1)}-x^{(k)}+\tau \nabla h(x^{(k)})-\tau \nabla h(x^{(k+1)}))).\) 
